Method and composition for cadmium plating



Patented Jan. 10, 1939 PATENT OFFICE 2,143,760 METHOD AND COMPOSITION FoR Leroy Camel,

CADMIUM PLATING Maple Heights, Ohio, assignor to The Plating and Galvanizing Company, Cleveland, Ohio, a corporation of Ohio No Drawing.

Application December 11, 1936,

Serial N 0. 115,349

12 Claims.

This invention, as indicated, relates to a meth- 0d and composition for cadmium plating, especially in relation to ferrous articles. More particularly, it comprises a composition having a combination of elements adapted to bring about bright plating of cadmium or cadmium associated with other metals or alloys and providing a method adaptable for quantity production with a product of uniform able finish,

Various types of cadmium plating compositions and processes are known, but many of these are not adapted for commercial use, either because of cost or intricacy of, handling, or by reason of difliculty in maintaining uniformity of product.

The present invention utilizes a cyanide bath as the electrolyte and includes with the same, small quantities of compounds to improve the conductivity of the bath and to bring about a bright coating upon the articles being plated. It has been found that the cyanide bath in general results in the best quality of color for the product, but in, many instances the time factor of the operation has been poor or the control of the operation has been difficult. With the composition herein described, it has been found that a uniformly high rate of production can be maintained and a cadmium coating of high luster maintained on the product, withno unfavorable factors to be taken into account as to the maintenance of the bath or excessive cost or complication in carrying out the process.

The process, while adapted to be carried out in certain proportionate relations between the elements entering into the same, is by no means restricted to certain critical proportions, but has a reasonable range of limits as to quantities, as well as to substitution of equivalent elements.

The compounds used for the electrolyte may comprise the following substances in proportions varying between the limits indicated:

Sodiumcyanide 10 to 15 ounces per. gallon of water Cadmium oxide or hydrate do 4 to' 7 Sodium sulphate do 3 to 6 Sodium sulphite do .25 to 1 Silver or cobalt salts do .133 to .2 Tung oil d0 .25 to 1 Water gallon 1 As a thoroughly tested cadmium plating bath quality and dependfor producing high luster cadmium coatings, the

following formula is set forth:

Sodium cyanide ounces per gallon of water 13 Cadmium oxide do 5 Sodium sulphate do 5.2 Sodium sulphite do .25 Silver nitrate do .133 Tung oil do .25 Water gallon 1 While tung oil is preferred as an addition agent, other oils such as cod liver oil or the like may be utilized, the oil preferably being an oil having a high degree of tenacity in the .form of a thin film.

Likewise, while a small amount of silver is found most effective in securing a bath having a high production efliciency, it has been found that cobalt may also be used satisfactorily. The 20 quantities set forth, as stated, are not critical.

If desired, however, a mixture in dry form of all of the ingredients except the tung oil may be prepared, such ingredients being added to the Water which may be very moderately heated to assist in the full dissolution of the powdered material and thereafter the tung oil added to such solution.

The bath, when fully prepared, will be found to *permit the use of a current of up to amperes 'herent to the surface treated, of fine grain, and

of smooth bright'texture.

The articles when plated as above outlined may be utilized for many purposes as a final coating without .bufiing or finishing treatment of any character, or the coating so provided may form a base coating for a finishing coat of other metal such as nickel or the like.

and suspending in said bath at the respective terminals of the plating circuit acadmium anode and the article to be plated. g

2. A composition of matter adapted for use in forming an electrolyte for the electrodeposition of cadmium, consisting of substantially 13 ounces of sodium cyanide, 5 ounces of cadmium oxide, 5.2 ounces of sodium sulphate, .25 ounce of sodium sulphite, .133 ounce of silver nitrate, and .25 ounce of tung oil to each gallon of water used for said electrolyte.

3. The process of electrolytically coating a fervrous article with cadmium in an alkali cyanide solution which consists in passing an electric current through said article as a cathode in the presence of a cadmium anode and an electrolyte containing sodium sulphite and a silver salt in less amount than any other substance in said electrolyte, said electrolyte containing an addition agent in the form of an oil of high film tenacity from a group-consisting of tung oil and cod liver oil.

4. The process of electrolytically coating a ferrous article with cadmium in an alkali cyanide solution which consists in passing an electric current through said article as a cathode in the presence of a cadmium anode and an alkali cyanide electrolyte containing sodium sulphite and an addition agent iromthe group consisting of tung oil and cod liver oil.

5. In the art of cadmium plating, the process which comprises electroplating cadmium from an alkali cyanide bath containing sodium sulphite in the presence of an addition agent selected from the group consisting of tung oil and cod liver oil. 6. In the art of cadmium plating, the process which comprises electroplating cadmium from an alkali cyanide bath in the presence of sodium sulphite, a metallic salt from the group consisting of silver and cobalt, such salt being in amount less than any other substance in said electrolytic bath, and an addition agent from the group consisting of tung oil and cod liver oil.

'7. The process of producing bright smooth coatings of cadmium on ferrous articles in an alkali cyanide solution which comprises the ,steps of adding to the electrolytic bath sodium sulphite and an oil of high film tenacity from a group consisting of tung oil and cod liver oil and suspending in said bath at the respective terminals of the plating circuit a cadmium anode and the article to be plated.

8. A sodium cadmium cyanide bath for electroplating with cadmium or cadmium associated with other metals comprising in combination sodium sulphite to the amount of approximately .25 ounce per gallon of water, an oil selected from the group consisting of tung oil and cod liver oil, and a salt of silver adding electrical conductivity to said bath.

9. In a sodium cadmium cyanide bath for electroplating with cadmium or cadmium associated with other metals, the combination of tung oil to .phite to the amount of approximately .25 ounce per gallon of water and tung oil to the amount of approximately .25 ounce per gallon of water.

11. In a sodium cadmium cyanide bath for electroplating witli cadmium or cadmium associated with other metals, the combination of sodium sulphite to the amount of approximately .25 ounce per gallon of water, tung oil to the amount of approximately -.25 ounce per gallon of water, and silver nitrate to the amount of .133

.ounce per gallon of water.

12. A composition of matter'adapted for use in forming an electrolyte for the electrodeposition of cadmium consisting, for each gallon of water to be used, of the proportion of 10 to 15 ouncesof sodium cyanide, 4 to 7 ounces of cadmium com- LEROY CAIWEL. 

